Log a version and latest commit hash on startup

Commit hash is set on build.

Author: Blagoj Atanasovski

Dockerfile

@@ -1,13 +1,15 @@
 # Build stage
 FROM golang:1.14.1-alpine AS builder
-COPY ./pkg timescale-prometheus-connector/pkg
-COPY ./cmd timescale-prometheus-connector/cmd
-COPY ./go.mod timescale-prometheus-connector/go.mod
-COPY ./go.sum timescale-prometheus-connector/go.sum
+COPY ./.git timescale-prometheus/.git
+COPY ./pkg timescale-prometheus/pkg
+COPY ./cmd timescale-prometheus/cmd
+COPY ./go.mod timescale-prometheus/go.mod
+COPY ./go.sum timescale-prometheus/go.sum
 RUN apk update && apk add --no-cache git \
-    && cd timescale-prometheus-connector \
+    && cd timescale-prometheus \
     && go mod download \
-    && CGO_ENABLED=0 go build -a --ldflags '-w' -o /go/timescale-prometheus ./cmd/timescale-prometheus
+    && GIT_COMMIT=$(git rev-list -1 HEAD) \
+    && CGO_ENABLED=0 go build -a --ldflags '-w' --ldflags "-X main.CommitHash=$GIT_COMMIT" -o /go/timescale-prometheus ./cmd/timescale-prometheus
 
 # Final image
 FROM busybox

cmd/timescale-prometheus/main.go

@@ -142,17 +142,19 @@ func main() {
 	cfg := parseFlags()
 	err := log.Init(cfg.logLevel)
 	if err != nil {
+		fmt.Println("Version: ", Version, "Commit Hash: ", CommitHash)
 		fmt.Println("Fatal error: cannot start logger", err)
 		os.Exit(1)
 	}
+	log.Info("msg", "Version:"+Version+"; Commit Hash: "+CommitHash)
 	log.Info("config", util.MaskPassword(fmt.Sprintf("%+v", cfg)))
-
 	http.Handle(cfg.telemetryPath, promhttp.Handler())
 
 	elector, err = initElector(cfg)
 
 	if err != nil {
-		log.Error("msg", "Aborting startup because of elector init error: %s", util.MaskPassword(err.Error()))
+		errStr := fmt.Sprintf("Aborting startup because of elector init error: %s", util.MaskPassword(err.Error()))
+		log.Error("msg", errStr)
 		os.Exit(1)
 	}
 

cmd/timescale-prometheus/version_info.go

@@ -0,0 +1,6 @@
+package main
+
+var (
+	Version    = "0.1.0-dev"
+	CommitHash = ""
+)

docker-compose.yml

@@ -12,7 +12,7 @@ services:
     - 9090:9090/tcp
     volumes:
     - ./sample-docker-prometheus.yml:/etc/prometheus/prometheus.yml:ro
-  prometheus_postgresql_adapter:
+  timescale-prometheus-connector:
     build:
       context: .
     depends_on: